There is a need for a compactly structured beam addressable information disk drive system capable of fitting within the half height format of a personal computer drive bay. Provision must be made in such a system for mechanisms to provide the functions of properly positioning a relatively bulky storage disk cartridge in the drive system and of bringing the storage disk and a disk spindle drive mechanism into engagement for rotation of the disk during read/write operation. It is desirable that these functions be provided by motor actuated apparatus for smoothness and reliability of operation. It is also desirable that a single motor actuated drive be employed to conserve space utilization and minimize the number of components involved. However, the operations of loading and unloading the cartridge must be performed at points in time separate from the operations of engaging and disengaging the spindle drive and disk. It is therefore an object of the invention to provide a single motor actuated drive for the load mechanism of a beam addressable information storage disk drive system that is simple and low cost and that will provide different drive functions in a timed sequence to separate functional mechanisms in the drive system.